A Novel Topology of Multilevel Bidirectional and Symmetrical Split-Pi Converter

Abstract

The paradigm of smart grids has encouraged new developments of power electronics converters, for instance, in the perspective of renewables and electric mobility applications. Aligned with this perspective, this paper proposes a novel topology of a multilevel bidirectional and symmetrical (MBS) split-pi dc-dc converter. As a central distinguishing feature, it operates with three voltage levels in both dc sides (0, vdc/2, vdc), meaning that the voltage stress in each semiconductor is reduced when compared with the conventional split-pi converters, and it operates with controlled variables (voltage and current) based on the interleaved principle of operation, although it is not an interleaved split-pi converter. As demonstrated along the paper, the MBS split-pi converter can be controlled with current or voltage feedback in any of the dc interfaces, while the common dc-link voltage is controlled by the dc interface where the source is connected. The adopted current and voltage control schemes, as well as the pulse-width modulation, are presented and comprehensively explained. The validation is presented for the main operation modes, where it is possible to verify the claimed distinguishing features of the proposed MBS split-pi converter.

Modeling and Performance Assessment of the Split-Pi Used as a Storage Converter in All the Possible DC Microgrid Scenarios. Part I: Theoretical Analysis

“…In the case of a Split-pi converter operating with V 1 ≤ V 2 and connected to a stiff microgrid, (4) and ( 8) are still valid, but (5), ( 6), ( 7),( 9), ( 10) and (11), ( 12), ( 13) are replaced by ( 16), ( 17), ( 18), (19), (20) and ( 21), ( 22), (23), respectively.…”

“…As such, it is the dual topology of the cascaded buck-boost HBC that was analyzed in [7,10,11]. The Split-pi was initially developed for electric vehicles and patented in 2004 [12], and it is receiving increasing attention due to its distinct advantages [13][14][15][16][17][18][19][20]. It exhibits high efficiency, like the DAB, but with a reduced switch count (eight vs. four switches, of which, only two are actively commutated).…”

“…Only three papers in the technical literature proposed applications in which the Splitpi converter was not controlled using an open-loop [16,17,19]. The aim of [17] was to study a system in which the Split-pi interfaced a flywheel with a 12 V, 120 W DC bus connecting a photovoltaic generator with a passive load.…”

“…However, they considered the converter connected to a passive load and neglected the parasitic resistances. Finally, Monteiro et al considered a Split-pi converter with a multilevel structure and controlled current or voltage in any of the two ports in an open-loop, whereas the common DC-link voltage was controlled in a closed-loop [19]. Only a few details about the control systems were given because the study mainly focused on comparing the multilevel Split-pi topology and the interleaved topology of [20].…”

Modeling and Performance Assessment of the Split-Pi Used as a Storage Converter in All the Possible DC Microgrid Scenarios. Part II: Simulation and Experimental Results

“…Among the several topologies of bidirectional DC-DC power converters, the Split-pi is receiving increasing attention due to its distinct advantages such as high efficiency, reduced switch count, small reactive components and switching noise, as well as suitability for multiphase systems, at the only cost of non-isolated operation [19][20][21][22][23][24][25][26][27]. However, none of the previous works on the Split-pi focused on the connection to DC microgrids.…”